Ground Resonance

[Mercuriell]

Hey Vinger, great to hear your Banshee nearly with you )))

Chill out over the GR, it's a necessary compomise for an uber high speed machine and as long as you don't load up the disc at HS don't think you're gonna have a problem

[Vinger]

Ok maidened her this morning, sad to say four flights is all I will have until the ground resonance problem can be rectified.!!!!! Flew perfectly and really well, but every landing is a nerve wracking experience, maybe I'm just a "beginner"!!!!!!!!!!!

[ame]http://youtu.be/ldcrhHaRe48[/ame]

[marcosp]

Holly cr**! That's bad. I don't have that happen to mine at all. Just a barely noticeable shake as most helis do at some lower rpm.

[Mercuriell]

I don't get that either, is it worth experimenting with grip tightness or checking main blade balance ?

I land in IUP1 then flick TH keeping the pitch at zero, only when the blades have slowed right down do I dump on some negative collective to slow the rotor head

[abanihani]

Me too, mine does not seem to have this resonance, I am used though to fly with throttle hold switch as i don't fly normal mode. all flat throttle curves so to land i auto from around 1 meter height.

[helicraze]

Mine doesnt do that at all

[Vinger]

Originally Posted by Mercuriell

I don't get that either, is it worth experimenting with grip tightness or checking main blade balance ?

I land in IUP1 then flick TH keeping the pitch at zero, only when the blades have slowed right down do I dump on some negative collective to slow the rotor head

John, that is the way I have always landed all my helis, but the Banshee team has specifically called for ZERO pitch on spool down. Blades are within 1g of each other and the CoG is spot on.

Re blade tightness, I am using the old and trusted way of turning heli sideways and blades does not fold under their own weight.

BUT I think blade balance etc can be ruled out as it does not happen all the time, for instances this was once in four spool downs, really messing with my confidence in the heli.

[RJ]

Hi Vinger,

I don't have a Banshee, but I tend to agree with your earlier assessment that you could try changing the resonance frequency of the landing gear. Does the TDR landing gear fit? Or maybe you can glue two Banshee skids together to stiffen and change the frequency. I have had a ground resonance problem that was fixed by changing the landing gear (but it wasn't a Banshee).

[Heli G]

There's a lengthy thread on the Banshee site, but the non-owners can't see it and people are asking me what is going on, so just wanted to give some feedback.

Same thing happened on my Banshee, also spooling down on grass. Used CF to strengthen the skids and avoid the toe out flex issue...initial indications are that it helped but it does not resolve the spool down resonance problem, it only helps to reduce the impact.

According to Banshee the problem rpm is around 1400 and one should avoid hard surfaces. A lot of testing, blade balancing, landing surface assessments, FBL checks etc later and no definate solution has been found. Right now the recommendation is to land at an rpm between 1100-1300, thus avoiding 1400...so more testing need to happen. The Banshee team is also geared to assist in resolving this problem. One way to replicate the resonance problem on grass is landing on hard surfaces and one of the owners suggested that the team focuses on this known issue to see what can be done. This is a great suggestion and I trust that a resolution would be found soon.

Flew the Banshee yesterday again and it is an awesome machine...incredibly fast, light and agile. I've only done a bit of 3D with it, but can't wait to smack it...just need to fix this spool down issue first and get more comfortable with it.

[helicraze]

I spool down at 0 deg and mini auto every landing, no issue

[Stolla]

Did some resonance testing today, landed on different surfaces from thick soft grass to very hard dusty type of surfaces, i.e like on marbles, landed deliberately in normal 1800 headspeed, touchdown, slight negative just to keep it there, i was expecting the worse tbh after seeing Peter and Gerards issues, BUT nothing, not even the slightest movement, just sits there and spooldown like its in a vice. My verdict, its a vbar issue, either setting or compatibility issue on a specific setting. I would not waste time looking for mechanical issues if you have resonance issues. After this test i'm absolutely 100% convinced its the fless system causing the deathshake, so sure that as i also offered on bshee forum i will bet a banshee on it! Off course im using beast, but you guys knew that, and im not saying you should sell your vbars, seems they work well for some. But i have seen it many times where vbars will react different to vibrations on the same machine, even the same versions. My recomendation, try a beast if you have issues, even if you have to borrow one, just make sure you lower cyclic limit to 11.5 degrees max as default will give you about 16 which will cause pitching.

[Vinger]

Thanks Stolla, just another nail in the coffin of my Banshee, I am sure it is possessed!! Have a BeastX handy will try that once I can source a PowerJive quickly, done with HeliJive and it's vulnerability.

[Heli G]

Did some more test flying today and no problems. So what has changed?

1) Using low head speed of 1300 to land...spoolup still on high head speed i.e. 1800-2200.
2) Modified the skids by adding a strip of carbon along the skid pipes which reduced the toe out flex.
3) Using stock default vbar settings.

I'm pretty sure it has to do with the grass we are landing on at a friend's wine farm where we are flying. The grass is very thick and has a very spongy/springy texture. This is been made worse by the heat wave which has dried out the grass quite a bit as well, exacerbating the "spring" effect. It also explains why the oscilation is not evident on each landing, which depends where you are landing and if you are landing on an "uneven" patch. I also think the skid mod has helped as I haven't had oscilations since doing the mod - Peter also did it on his machine and the landings today were without incident.

Things are looking good and I just need to log more flights on it to confirm. Flew at 2200 rpm today and what a thrill.

Originally Posted by Stolla

After this test i'm absolutely 100% convinced its the fless system causing the deathshake, so sure that as i also offered on bshee forum i will bet a banshee on it!

After today's incident free session you better pack up the Banshee mate...Peter has a BeastX and will be installing it to collect your Banshee.

[Stolla]

Well i never said vbar wont work, just imop its the cause if your problems, i.e not banshee problem, fact you have to modify skids and be careful where you land confirms my suspicion, you will find no worse or different tyoes of grass where we land, from very long and soft to short and hard and dust, wet and dry, ive done them all so unless the grass you land had been grown under labarotory conditions to specifically upset your machine i cant see how thats the cause, just my opinion off course, btw i said banshee, not my banshee, http://www.newegg.com/Product/Produc...9SIA0S507H4617, you think i'm nuts?!

[Vinger]

mmmmmmmmm, back pedalling already!!

Start worrying, HeliG is an advocate and according to him any post made on an open or closed forum is as good as a contract, so lawyers letter to follow

Just happy that we are getting closer to a solution for the problem we are having. Hopefully we can now start to enjoy our Banshee's.

[Ktmheli]

Originally Posted by Vinger

mmmmmmmmm, back pedalling already!!

Start worrying, HeliG is an advocate and according to him any post made on an open or closed forum is as good as a contract, so lawyers letter to follow

Just happy that we are getting closer to a solution for the problem we are having. Hopefully we can now start to enjoy our Banshee's.

Glad you and HeliG are winning now. Awesome news.

[Heli G]

Originally Posted by Stolla

Well i never said vbar wont work, just imop its the cause if your problems, i.e not banshee problem, fact you have to modify skids and be careful where you land confirms my suspicion, you will find no worse or different tyoes of grass where we land, from very long and soft to short and hard and dust, wet and dry, ive done them all so unless the grass you land had been grown under labarotory conditions to specifically upset your machine i cant see how thats the cause, just my opinion off course, btw i said banshee, not my banshee, http://www.newegg.com/Product/Produc...9SIA0S507H4617, you think i'm nuts?!

Hermann, when our courts interpret a contract they consider the context in which it was made...a "bet" made in the LTD Banshee forum will presume "the Banshee" you offered is the actual LTD edition and not just any random coaxial heli which you now reference. Our courts also presumes that it was not the intention to mislead, so if you did mean a cheap coxial heli the presumtion is that you would have stated this intention, specifically since the term Banshee iro it being used in the Ltd Banshee forum refers to the LTD edition. A further point is your absolute conviction "10000%" with which you placed the "bet", which further presumes you were sure enough of your theory to place a Ltd Banshee at risk, negating the argument of "you think i'm nuts". I am afraid the onus will be on you to prove otherwhise. Of course Hermann, we are all "heli freak friends" so this is just some light hearted humour.

Untested theories are abound as to the oscillations and what we have done was painstakingly eliminate those we had control over and offer the facts. Interestingly enough a friend also picked up an oscillation yesterday on the same landing spot and he is flying a BeastX on his 6HV. Right now we seem to have a solution, but I am keen to do further tests. How much the landing skid mod has contributed is difficult to say. One thing I like about it is the reduction of toe out flex which offers more stability. I would still like to see what the BeastX does on the Banshee, if only to satisfy my own curiosity.

[Stolla]

Well you never accepted my bet vinger suffice to say i will spell out the terms if you want which is the coaxial i posted, read i said i will bet so still have to, ok what are you bringing to the deal, surely you have to put something on the table, or is this one sided bet? Lol

[lotus7]

Originally Posted by Heli G

. Interestingly enough a friend also picked up an oscillation yesterday on the same landing spot and he is flying a BeastX on his 6HV.

OT ( and apologies), but since it was mentioned .....
The 6HV oscillation was caused by a little gust coming through as I was putting her down already on TH, getting the heli a bit unstable and the tail fin got stuck in that grass Heli G mentioned earlier. This disturbed the balance and caused the oscillation/resonance

The ground resonance problems with the 6HV was always at spool up with a not so soft start up , mostly on HW ESC's .
None of the 5 6HV's at this field have had the spool up resonance tendencies reported elsewhere.

[Vinger]

The bet was always that I put a BeastX on my Banshee, if problem goes away we are all happy, if not then you Banshee is mine!!!! You get the bragging rights that a Beast is better at handling ground resonance.........